Kansas' 4th Congressional District and Georgia's 6th District have been in Republican hands for decades, but just in recent weeks Democrats have gained steam forcing the GOP to run hard and switch to defense in reliably red districts.

This month's special elections have Republicans and Democrats looking ahead eagerly to the 2018 midterm, with conservatives now wide awake to the reality that they are fighting to hold a majority in the face of a highly mobilized liberal base and a president whose approval ratings have fallen to historic lows so early in his term.

On Tuesday, voters in the Wichita-based 4th District of Kansas will cast their ballots to elect the replacement for former Rep. Mike Pompeo who joined President Donald Trump's administration as the new head of the Central Intelligence Agency. Next week, on April 18, voters in Georgia will fill the seat vacated by Trump's new Health and Human Services (HHS) Director Tom Price.

To keep their majority in the House, Republicans need to defend 24 seats in 2018. Their majority in the Senate looks more secure as their Democratic counterparts have to hold on to 25 seats, ten of which are in states Trump carried. Yet this week top GOP officials began scrambling to fundraise and push voter turnout in two traditionally safe districts ahead of the upcoming special elections.

As polls were opening for the Tuesday special election in Kansas, President Trump took to Twitter to endorse the Republican candidate and state treasurer, Ron Estes, who has found himself in a much closer-than-expected race against Democrat Jim Thompson, a civil rights attorney and U.S. Army veteran. The tweet was not the only presidential endorsement. On Monday, Trump recorded a robocall endorsing the Republican candidate, telling voters that "Ron is going to be helping us big league."

On top of the president's support, over the weekend, Vice President Mike Pence also recorded a robocall, Texas Republican senator Ted Cruz stumped with Estes, and Speaker of the House Paul Ryan (R-Wisc.) sent out a fundraising letter calling on GOP voters to "help strengthen our House majority."

According to The New York Times, that the last-minute GOP campaign sprint followed some troubling poll numbers showing Estes winning by single digits. That narrow gap sparked concerns that a district that Donald Trump carried by almost 30 points in November, that is also the home of Koch Industries, the multi-billion dollar corporation run by deep-pocket Republican donors Charles and David Koch, could be in play.

Right around the corner on April 18th, Georgia's 6th District, which includes some northern suburbs of Atlanta and parts of Cobb and Fulton County, will hold their special election. The district which was consistently leaning Republican in the polls suddenly switched this week, according to the Cook Political Report which changed that outlook from leaning Republican to a toss-up. If a clear winner does not emerge with at least 50 percent of the vote, the race could wind up in a run-off election that would be held on June 20.

Republican donors are looking at a disparate field of 11 candidates led by former Georgia Secretary of State Karen Handel who are battling one another for Tom Price's seat. On the Democratic side, investigative film maker and former congressional aide Jon Ossoff has enjoyed the benefit of his divided opponents along with a massive fundraising advantage. With the help of very generous national party donations, the 30-year-old candidate raised an impressive $8.3 million the first quarter, most of which came in from out of state.

Even though the Republicans have occupied the Georgia seat since Newt Gingrich's first election victory in 1979, the last election was arguably too close for comfort, with Trump winning the district with a slim one-percent margin.

Special elections have rarely been a consistent predictor of things to come in midterm elections, but when two traditionally red districts start to turn, it's time for the GOP to worry.

Senior elections analyst for RealClearPolitics, Sean Trende warned that today's election in Kansas could spell trouble for Republicans, even if they win. "[I]f Thompson wins, or even makes it a close race, it would be evidence that the Democratic enthusiasm that we saw in blue areas of the country might be present in other areas too, and that Republicans should start sweating 2018," he said referring to the massive protests in "liberal enclaves" around the country.

The early special elections will be a testing ground to see if the enthusiasm demonstrated in nation-wide protests "will translate into votes in red areas of the country," Trende writes. Kansas and Georgia will be the first tests, followed by special elections in May to fill the seats of South Carolina's 5th District representative Mick Mulvaney, now Trump's budget director, and Montana's representative Ryan Zinke, who now heads the Department of the Interior.

Trends in voting behavior show the party that holds the White House usually has a disadvantage during midterm elections and special elections, which could spell trouble for Trump and the Republican Party. A president who is doing well in the polls and overseeing a booming economy can usually help defend seats and sometimes win an extra handful, but those conditions reflect the best circumstances.

According to Jon Fortier, director of the Bipartisan Policy Center's democracy project, election-watchers should pay closer attention to those historic trends than this month's special elections. "It's obviously something of a worry if they lose some of these seats, it will be a warning sign," he said, "but just because they lose one, it might not be a sign of things not going well." There are more predictive factors at play.

Republicans already enjoy something of an advantage as their voters tend to turn out in greater numbers during midterm elections. Of course, there are always exception. In a year like 2006, House Democrats were able to mobilize against a very unpopular President George W. Bush and won 28 GOP-held seats. In that context, winning back 24 seats in 2018 could be doable for Democrats.

"Midterms and special elections are often reactions against the president," Fortier explained, "but I think the big question is what does Trump look like in the June of 2018, not what he looks like today." As the Trump presidency progresses over the next year, those developments will contribute much more to the outcome in November 2018.

"If the economy and the Trump presidency are going up in that period of time, then whatever happened in these elections today won't matter that much and really it's the conditions on the ground as we go into that midterm election that will really matter," Fortier said.

The outcome of special elections is rarely a reliable predictor of what things may come in the midterm elections, though if Democrats are able to close the gap in Kansas and win in Georgia, their forecasts for a House majority are likely to look a lot rosier.

Associate editor of Sabato's Crystal Ball at the University of Virginia Center for Politics, Geoffrey Skelley, warns against "over-interpreting" the results of the upcoming House contests.

"Special elections are just that, they are special," he said. "It's important to not make major assumptions about November 2018 based off the results of the next few weeks and these elections. It may be harbinger but it may not."

But given the current circumstances, with a president polling at 40 percent approval and a limited amount of time to push his agenda through a Republican-controlled House and Senate, the GOP should be worried.

"If recent history is any guide, controlling everything is great, but it often doesn't last very long," Skelley said. "So if you're going to be smart about it politically, you should be trying to get as much done as possible in the first few years because you might not have any more time than that."

Even if Democrats are able to eke out a victory in Georgia and even potentially in Kansas, that should not be taken as any guarantee that they will take back the House or the Senate.

There are a lot of contingent event that could happen," Skelley advised, Trump's approval rating could be in the 60 percent range, like Bush's was in 2002 when he held the GOP majority in the House and Senate. "But no one can predict. We are a long way from November 2018."